To clarify a comment I made earlier...
In my specific circumstance (lots of small files grouped in large quantities in single directories), I am unhappy with the performance of the F540 that I have. NetApp tech support and I have been working on the issue for almost 3 months now, and resolution may be in sight.
As to the hardware itself, it's nice stuff, fast, reliable, easy to care for, couldn't ask for anything more.
So if your situation is similar to mine, the NetApp may not be the optimal choice.